What is the value of (x + y)^4 ?

Question

What is the value of (x + y)^4? (1) The product of x and y is 7. (2) x and y are integers. Modified from: what-is-the-value-of-x-y-128238.html

asterixmatrix · Answer

1. insuff as x and y can have lot of different values ( x= 1 y =7 , or x=1/7 and y = 49)
2. insuff as x and y can be any integer (x=1 y=2, x= -4 y=4)

taking both we know xy =7 and are integers. Only values satisfying this is x= -1 and y =-7 or x=1 and y=7 (values can be interchanged)
so we get (-1 + -7)^4 or (1+7)^4 which gives the same value. hence C is suff

Economist · Answer

It is essentially the same as the previous non-modified version. Ans should still be C. Or is there a vicious trap !